Extracellular nucleotides liberated at inflammatory tissue sites are metabolized to adenosine by surface expressed ecto-nucleotidases (CD73 and CD39). Ongoing studies indicate that adenosine liberated by this process is available to activate surface adenosine receptors (A1AR, A2AAR, A2BAR, A3AR), and has been shown to attenuate acute lung injury. In the present study, we will use in vitro models of mechanical stretch and murine ventilator induced lung injury to study adenosine-tissue protection during ALI. Preliminary studies indicate a contribution of pulmonary CD39 and CD73 as control points for generation of extracellular adenosine during VILI. Moreover, studies in gene-targeted mice for individual ARs suggest a prominent role of A2BAR signaling for lung protection during VILI. Thus, we will pursue work toward: A) Defining details of extracellular adenosine generation during mechanical stretch or VILI; B) Define transcriptonal regulation and consequences of signaling through ARs during VILI; and C) Extend evidence for a role of adenosine generation and signaling as therapy of VILI. We expect that these studies will shed new light on molecular mechanisms through which cyclic stretch as occurs during mechanical ventilation elevates extracellular adenosine levels as a tissue protective mechanism. We will have developed strategies that utilize these mechanisms to attenuate inflammation and capillary-alveolar leakage during VILI. Taken together, these studies will lay the groundwork for novel and specific therapeutic approaches in the treatment of acute lung injury.